The zoogeography of the montane forest avifauna of eastern Tanzania - Biogeography and Ecology of the Rain Forests of Eastern Africa - page 213

n overiew of the Easten Tanzanian
montane forest avifaunas

Diversiy and enemsm in the East Coast
scarpment oress

In terms of species composiion, therefore, the
East Coast Escarpment forests consitute one of
the seven disinct Groups of African montane avi-
faunas. This disincive East Coast Escarpment
montane forest avifauna, which we discuss in the
remainder of this chapter, can be considered to
range from the Usambaras in the north to the
Nyika and Viphya Plateaux in the south (see
Figure 10.2). It is likely that the Matengo High-
lands in southen Tanzania and the Njesi Plateau
in northen Mozambique also belong here,
though their avifaunas are not well known.
In this secion, we carry out an analysis of the
East Coast Escarpment avifauna, concentraing
on eight paricular sites. For half these sites, the
montane forest avifaunas are very well known, and
it is unlikely that many addiional species will be
found, for instance in the Usambaras, Ulugurus,
at Mufindi, or on the Nyika Plateau. The possi-
bility remains of one or two addiional species sill
being found in the East Uzungwas and Mount
Rungwe. The Nguru and Ukaguru avifaunas have
been slightly less well sampled (as indicated by the
discovery of the elusive lringa Ground-robin
Shppardia lowei in the Ukagurus in 1989: N. E.
Baker and E. M. Boswell, in it.), but even in
these sites it is unlikely that more than a handful
of montane forest species remain unrecorded.
Despite the incompleteness of the data, we doubt
that any new discoveries in the Ngurus or Uka-
gurus will result in significant changes to the con-
clusions we make in this chapter. There are, of
course, several other mountain ranges in easten
Tanzania that are too poorly known to be
included in this analysis. These include the Pare
Mountains, Rubeho Mountains, Mahenge High-
lands, Njombe Highlands, Kipengere Mountains,
Livingstone Mountains, and Matengo Highlands.
The picture painted in this chapter is the best
possible on available data; further eploraions
will inevitably result in new surprises.

Fifty-seven montane forest species are known
from the East Coast Escarpment forests, of which
16 are endemics (i.e. occurring nowhere else) (see
Table 10.2). This level of diversiy is similar to
that of the Cameroun and Central East Africa
Montane Forest Groups, and much higher than
that of the species-poor Ethiopia, South Malawi
and south of Zambezi Groups. The East Coast
Escarpment Group is, however, impoverished in
comparison with the Alberine Rift Group, which
has 87 montane forest species, 32 of them
endemics (see Table 10.2). In terms of the num-
bers of endemic species, the East Coast Escarp-
ment is one of the three major cenres in Africa,
along with Cameroun and the Alberine Rift
(Ethiopia represening a smaller cenre of
endemism).
Table 10.4 presents data on eight forests within
the East Coast Escarpment Group for which the
avifaunas are well known. Basic inventory work on
these avifaunas has been described by Loveridge
(1922, 1933), Friedmann (1928), Sclater &
Moreau (1932-3), Bangs & Loveridge (1933),
Moreau (1935, 1940), Moreau & Moreau (1937),
Fuggles-Couchman (1939, 1984, 1986), Williams
(1951), Friedmann & Stager (1964), Ripley &
Heinrich (1966, 1969), Benson & Benson (1977),
Britton (1978, 1981), Dowsett & Dowsett-Lem-
aire (1979), Stuart (1980, 1981a, 1981b, 1983,
1985), Stuart & Turner (1980), Stuart & van der
Willigen (1980), Tuner (1980), Stuart et al.
(1981, 1987), Stuart & Jensen (1981, 1985), van
der Willigen (1981), Jensen & Stuart (1982), Jen-
sen (1983), Dowsett-Lemaire (1989) and Jensen
& Brogger-Jensen (1992).
In terms of species diversity, these forests have
between 27 and 42 montane species, the highest
diversity being in the Usambaras, Ulugurus and
Easten Uzungwas (Mwanihana and Chita).
There is a general trend to decreasing diversity
with increasing distance from the Equator (from
Usambara 5° S) to Nyika Plateau (

11° S).
Another rend is for higher diversity in areas of
high annual rainfall, such as Usambara and Ulu-

c. c.